Configuring Dhcp Snooping - 3Com 4500 Configuration Manual

When receiving a DHCP client's request without Option 82, the DHCP snooping device will add the
option field with the configured sub-option and then forward the packet. For details, see
Table 3-2 Ways of handling a DHCP packet without Option 82
Sub-option configuration
Neither of the two sub-options is
configured.
Circuit ID sub-option is configured.
Remote ID sub-option is configured.
The circuit ID and remote ID sub-options in Option 82, which can be configured simultaneously or
separately, are independent of each other in terms of configuration sequence.
When the DHCP snooping device receives a DHCP response packet from the DHCP server, the DHCP
snooping device will delete the Option 82 field, if contained, before forwarding the packet, or will directly
forward the packet if the packet does not contain the Option 82 field.

Configuring DHCP Snooping

Configuring DHCP Snooping
Follow these steps to configure DHCP snooping:
To do...
Enter system view
Enable DHCP snooping
Enter Ethernet port view
Specify the current port as a
trusted port
The DHCP-Snooping device will ...
Forward the packet after adding Option 82 with the default
contents.
The format of Option 82 is the one specified with the
dhcp-snooping information format command or the default
HEX format if this command is not executed.
Forward the packet after adding Option 82 with the configured
circuit ID sub-option in ASCII format.
Forward the packet after adding Option 82 with the configured
remote ID sub-option in ASCII format.
Use the command...
system-view
dhcp-snooping
interface interface-type
interface-number
dhcp-snooping trust
3-4
Table
Remarks
—
Required
By default, the DHCP snooping
function is disabled.
—
Required
By default, after DHCP
snooping is enabled, all ports of
a switch are untrusted ports.
3-2.